ION-TRANSFER CURRENT-SCAN POLAROGRAPHIC STUDIES OF METAL EXTRACTANTS WITH ASCENDING WATER ELECTRODE - TRANSFER OF DIVALENT METAL-ION COMPLEXES OF PHENANTHROLINES ACROSS A LIQUID-LIQUID INTERFACE

The transfer mechanism of Ni2+, Co2+, Zn2+ and Cd2+ ions from an aqueous to a dichloroethane (DCE) solution of phenanthroline derivatives (Phen) was studied. Included were 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (4,7-DMP), 4,7-diphenyl-1,10-phenanthroline (4,7-DPP) and 2,9-dimethyl-1,10-phenanthroline (2,9-DMP). The investigation was carried out by current-scan polarography at the ascending water electrode (AWE). Some polarographic waves were observed that can be attributed to the slow formation of 1:1 M2+-Phen complexes. In some cases, as with the Ni2+-Phen systems and the Co2+-4,7-DPP system, no wave was observed, because the complexation rates are too slow. All of the Cd2+-Phen and all of the Zn2+-Phen systems, except for the Zn2+-4,7-DPP system which exhibits a kinetic wave, yielded diffusion-controlled waves. Furthermore, a number of these systems appear to be affected by significant interfacial adsorption of the M2+-Phen complexes.